1. Field of the Invention
The present invention relates to configuration and control of a conveyance apparatus in a recording apparatus that holds and conveys a recording medium with a conveyance unit and performs a recording operation.
2. Description of the Related Art
Image forming apparatuses (e.g., copying machines and printers) have been recently used to print photo images in many cases. Especially, an inkjet image forming apparatus has the capability of forming a high-quality image comparable to a silver-halide photo due to minimization of ink droplet or improvement in image processing technique.
To satisfy requirements for such high-quality images, high accuracy is required in the conveyance of a recording medium. A large problem in improving the conveyance accuracy is a periodic conveyance deviation that may derive from fluctuations occurring in a driving transmission unit (e.g., conveyance rollers and gears). In a case where a recording medium is conveyed by a driving transmission unit that causes large fluctuations, the conveyance amount of the recording medium periodically varies even when the rotational amount is constant. The image quality is dissatisfactory because of deterioration in the conveyance accuracy. To solve the above-mentioned problem, very high accuracy is required in manufacturing mechanism parts that constitute the recording apparatus.
However, the degree of improvement in the manufacturing accuracy is limited. Pursuing high accuracy in the manufacturing of mechanism parts will increase manufacturing costs significantly. Therefore, it is conventionally proposed to actually measure the conveyance amount for each rotational phase interval after each recording apparatus is manufactured and then obtain a correction value for the rotational amount of the conveyance roller based on a measurement result.
More specifically, a periodic conveyance variation amount correcting method, which includes acquiring a fluctuation amount or a periodic conveyance variation amount (i.e., an integration of fluctuations with respect to a predetermined rotational phase interval) of a conveyance roller based on actual measurement and correcting the conveyance amount based on the acquired value, is conventionally proposed. As discussed in Japanese Patent No. 3988996, it is conventionally known to prepare a print pattern usable to actually measure the fluctuation amount of a conveyance roller beforehand and acquire a fluctuation amount based on the pattern.
Further, it is conventionally known to predict a periodic conveyance variation amount based on the acquired fluctuation amount of the conveyance roller and the rotational position of the conveyance roller, in an actual printing operation, and correct the rotational amount of the conveyance roller in such a way as to make the conveyance amount constant.
In general, a main recording unit of the recording apparatus includes a recording head and a plurality of conveyance rollers provided on the upstream side and the downstream side of the recording head. The recording apparatus performs an image recording operation in the entire area of a recording medium. Therefore, the recording apparatus switches between a state in which only a single conveyance roller is operative to convey the recording medium and a state in which a plurality of conveyance rollers is cooperative to convey the recording medium.
Therefore, if the method discussed in Japanese Patent No. 3988996, which includes the conveyance variation amount prediction and the roller rotation correction, is employed for a recording apparatus that includes a plurality of conveyance rollers, it is feasible to correct the periodic conveyance variation amount in a state where the conveyance is performed using a single conveyance roller. However, it is unfeasible to perform the periodic conveyance variation amount correction in a state where a cooperative conveyance by a plurality of conveyance rollers is performed. Therefore, in an area where two or more conveyance rollers are cooperative to convey a recording medium in the recording apparatus that includes a plurality of conveyance rollers, a correction value to be applied to the conveyance when carried out by a single conveyance roller is used to perform the periodic conveyance variation amount correction.
As a result, increasing the conveyance accuracy in a cooperative conveyance state using a plurality of conveyance rollers is difficult even when the periodic conveyance variation amount correction is performed. The image quality in the corresponding area cannot be improved.